Prolonged pressor responses to intravenously injected vasopressin in anaesthetized Brattleboro rats

Randomized intravenous injections of arginine vasopressin, 0.02 to 0.62 micrograms/kg, administered to anaesthetized Brattleboro rats genetically lacking vasopressin, produced significantly greater, prolonged dose-dependent pressor responses than those produced in normal animals of the parent Long-Evans strain. Dose-related decreases in cardiac output were transient in both groups of animals but were greater in Brattleboro rats. It is concluded that the enhanced pressor effects in these animals were associated with greater and prolonged increases in the total peripheral resistance.